Trench Junction Barrier Schottky Rectifiers (TJBS Rectifiers) and Trench MOS Barrier Schottky (TMBS rectifiers) are well known structures capable of sustaining breakdown voltage higher than the theoretical Silicon limit in a planar structure. As will be later seen in the novel structure of the invention, the trenches are filled with doped polysilicon or other semiconductor material with an n or p doping concentration. The proposed structure also incorporates buried oxide regions into the trenches and the Schottky interface is formed at the tops of the mesas.
It would be desirable to increase the blocking voltage of such devices, or keeping the same breakdown voltage as that of a planar Schottky, but reducing the forward voltage drop by lowering the material thickness and resistivity.
With reverse bias applied, the TMBS, like the TMBS, is capable of sustaining a blocking voltage higher than Silicon's theoretical limit and is characterized by two effects: firstly, the Electric Field at the Schottky/Silicon interface is significantly reduced; secondly the Electric Field critical peak moves from the Schottky interface, down to the silicon drift region. The decreased field at the Schottky interface leads to a decrease in reverse leakage current due to the absence or reduction of the Barrier lowering effect. Further, the shift of the Electric Field peak away from the Schottky interface increases the ability of the mesa to sustain a blocking voltage greater than the theoretical blocking capability. The TJBS efficiency depends on the trench depth, the polysilicon doping concentration and the mesa width.
However, the blocking capability of the trench barrier Schottky is limited by punch-trough phenomena in the depletion layer at the transition zone between epi and substrate, that may lead to a premature breakdown voltage and limits the blocking capability of the elemental cell of the device.